Systems with high density packing of micromachines

ABSTRACT

Micromachine systems are provided. An embodiment of such a micromachine system includes a substrate that defines a trench. First and second microelectromechanical devices are arranged at least partially within the trench. Each of the microelectromechanical devices incorporates a first portion that is configured to move relative to the substrate. Methods also are provided.

BACKGROUND OF THE INVENTION SUMMARY OF THE INVENTION

[0001] Briefly described, the present invention relates tomicromachines. In this regard, embodiments of the invention may beconstrued as micromachine systems. An embodiment of such a micromachinesystem includes a substrate that defines a trench. First and secondmicroelectromechanical devices are arranged at least partially withinthe trench. Each of the microelectromechanical devices incorporates afirst portion that is configured to move relative to the substrate.

[0002] Other embodiments of the invention may be construed as methodsfor forming arrays of micromachines. In this regard, an embodimentincludes the steps of providing a substrate and forming a trench in thesubstrate. First and second microelectromechanical devices are arrangedat least partially within the trench. Each of the microelectromechanicaldevices includes a first portion that is configured to move relative tothe substrate.

[0003] Other features and advantages of the present invention willbecome apparent to one with skill in the art upon examination of thefollowing drawings and detailed description. It is intended that allsuch features and advantages be included herein within the scope of thepresent invention, as defined in the appended claims.

FIELD OF THE INVENTION

[0004] The present invention generally relates to micromachines and,more specifically, to systems and methods that provide high densitypacking of micromachines on a substrate.

DESCRIPTION OF THE RELATED ART

[0005] Micromachines, such as microelectromechanical system (MEMS)devices, are becoming prevalent in numerous applications. These devicesare able to provide mechanical functionality on an extremely smallscale. For example, a typical micromachine can be formed on the scale oftens of nanometers to millimeters.

[0006] Oftentimes, micromachines are formed on substrates, e.g., asemiconductor wafer. A single substrate can include hundreds ofmicromachines or more. The number of micromachines that are able to beprovided per unit area of substrate, i.e., the packing density of themicromachines, is influenced by several factors. For example, the sizeof the micromachines and spacing provided between adjacent micromachinesaffect the packing density of the micromachines.

[0007] Since there is a seemingly perpetual desire to increase thepacking density of micromachines, there is a need for systems andmethods that address this and/or other desires.

DESCRIPTION OF THE DRAWINGS

[0008] The present invention, as defined in the claims, can be betterunderstood with reference to the following drawings. The drawings arenot necessarily to scale, emphasis instead being placed on clearlyillustrating the principles of the present invention.

[0009]FIG. 1 is a schematic diagram depicting a portion of a substrateincluding a representative arrangement of micromachines.

[0010]FIG. 2 is a schematic diagram depicting the micromachines of FIG.1.

[0011]FIG. 3 is a schematic diagram depicting a representativearrangement of micromachines.

[0012]FIG. 4 is a schematic diagram depicting a representativearrangement of micromachines.

[0013]FIG. 5 is a schematic diagram depicting a portion of a substrateincluding an representative arrangement of micromachines.

DETAILED DESCRIPTION OF THE INVENTION

[0014] Referring now to the figures wherein like reference numeralsindicate corresponding components throughout the several views, FIG. 1depicts an embodiment of a micromachine system 100. As described ingreater detail hereinafter, embodiments of the micromachine system ofthe present invention can employ various techniques for providing highdensity packing of micromachines.

[0015] In FIG. 1, micromachine system 100 includes multiplemicromachines 110 that are provided on a substrate 111. By way ofexample, substrate 111 can be a semiconductor wafer. Each micromachine110 incorporates a micromover component (“micromover”) 112. Micromovers112 are adapted to move relative to at least a portion of substrate 111.In other embodiments of the invention, various types of micromachinesother than micromovers can be used. However, in the description thatfollows, embodiments of the invention will be described with referenceto micromovers. This is done merely for ease of description and not forthe purpose of limitation.

[0016] Micromovers 112 preferably are spaced from each other so thatadjacent micromovers 112 do not interfere with each other. Morespecifically, if adjacent micromovers were permitted to contact eachother, either or both of the micromovers could be inhibited fromperforming their intended functions and/or could be damaged. Spacingbetween adjacent micromachines is accommodated by arranging eachmicromover within a corresponding trench 116. Preferably, each trench isdefined by material of substrate 111. More specifically, the material ofthe substrate forms a longitudinal barrier 118 between adjacentlydisposed micromovers of a row 120 of micromovers. A transverse barrier122 is formed between adjacently disposed micromovers of a column 124 ofmicromovers. Trenches 116 can be formed by either removing material ofthe substrate in the desired area of the trench, such as by etching,and/or by forming a raised area about the desired area of the trench,such as by deposition of material.

[0017] In the embodiment depicted of FIG. 1, micromovers 112 aresubstantially retained within their respective trenches by flexures 130.Multiple flexures 130 engage each micromover 112. The flexures tend tomaintain a micromover within its trench while permitting the micromoverto move, e.g., micromover 112 moves relative to substrate 111.Representative examples of flexures include springs and micro-fabricatedbeams.

[0018] Each flexure 130 is affixed to an anchor 132. Anchor 132 can beformed as a component affixed to the substrate or as a portion of thematerial of the substrate.

[0019] Micromachines can be fabricated by a variety of micromachiningprocesses. In a typical process, the device material is silicon that isprovided in the form of a wafer. The micromover, flexure, and anchorsystem are defined in the silicon wafer by a masking layer, which can beformed of a photoresist, for example. A deep silicon reactive ion etchmay be used to transfer the mask shape into the silicon wafer. A typicaletch depth may be 10 to 100

m. The etch depth is often set by an etch-stop layer that is provided inthe silicon wafer before micromachining fabrication is begun. Theetch-stop layer can be formed of silicon dioxide, for example. Theetch-stop layer is used as a sacrificial layer to facilitate the releaseof the micromover from the substrate. Release refers to a process bywhich constraints on the MEMS part, e.g., the micromover, are removed.This allows the micromover to move freely relative to the substrate. Inthe embodiment of FIG. 1, for example, flexures and anchors serve toconstrain the motion of the released micromover to the desired degreesof freedom.

[0020] An isotropic etch of the sacrificial layer is performed to removethe sacrificial material from about the micromachine components indesired areas. The sacrificial layer may be 1 Om thick, for example. Theduration of the etch step will determine which structures are releasedfrom the substrate. For instance, the longer the etch time, the moresacrificial material typically is removed during the etch. By removingmore material during the etch, typically a larger structure, i.e., thestructure defined in the masking step, can be released. Given sufficienttime, the release etch can completely remove sacrificial material formedunderneath a micromover and its flexures. In contrast, anchors are notreleased by the etch. To prevent release of the anchors, the anchors areformed sufficiently wide so that they are not undercut by the etch to adegree that permits release.

[0021] Referring now to FIG. 2, it is shown that several discretedimensions affect the packing density of the micromachines 110, i.e.,the number of micromachines per unit area. More specifically, eachmicromachine 110 exhibits a length (MX) and a width (MY), with MX and MYincluding both the dimensions of the physical device and its operatingrange. Each micromachine 110 is spaced from an adjacent micromachine bya length (SX), i.e., SX is the distance between adjacent micromachinesof the same row, and a width (SY), i.e., SY is the distance betweenadjacent micromachines of the same column. Thus, in the embodimentdepicted in FIG. 2, the total area associated with a micromachine 110 isdefined by:

MX+(2)(½ SX), in the X dimension; and

MY+(2)(½ SY), in the Y dimension.

[0022] An alternative embodiment of micromachine system 100 is depictedin FIG. 3. As shown in FIG. 3, longitudinal barriers, which are shown inthe embodiment of FIGS. 1 and 2, are not provided between adjacentmicromovers 110. In this configuration, an increased packing density ofthe micromachines is achieved compared to the embodiment of FIGS. 1 and2. More specifically, each micromachine 110 of FIG. 3 requires a lengthof MX1, i.e., in some embodiments, MX1

MX+(2)(½ SX).

[0023] Another embodiment of micromachine system 100 is depicted in FIG.4. As shown therein, separators 410 are provided between adjacentlydisposed micromachines. The separators 410 are adapted to prevent directcontact of adjacent micromovers. Preferably, each separator 410 isformed as a distinct component, i.e., the separator is not formedentirely of the material of the substrate. For example, separator 410could be a micro-fabricated beam that is similar to that of flexure 130.

[0024] In FIG. 4, anchors 420 are used to secure multiple flexures 130.In particular, each anchor 420 is arranged between an adjacent pair ofmicromovers and is used to affix at least one flexure from each of thepair of micromovers. Each anchor 420 also can secure one or moreseparators 410. In embodiments incorporating anchors for fixing multiplecomponents, such as flexures and/or separators, an increased packingdensity can be achieved. More specifically, in some embodiments, MX2

MX1

MX+(2)(½ SX).

[0025] In FIG. 5, micromachine system 100 includes multiplemicromachines 502 that are provided on a substrate 504. Micromachines502 preferably are spaced from each other so that adjacent micromovers506 do not interfere with each other. Flexures 508 of the micromachinesare affixed to anchors. The anchors, being raised from a surface 510 ofthe substrate, define a trench 512 that is arranged about the anchors.

[0026] In FIG. 5, four types of anchors are depicted, i.e., anchors 514,516, 518 and 520. More specifically, anchors 514 are adapted to affix aflexure from a single micromover. Typically, such a micromover isarranged at a corner of the array of micromachines. In regard to anchors516, these anchors are adapted to affix flexures from at least twomicromachines. Since micromachine system 100 of FIG. 5 includes columns522 of micromachines, anchors 516 typically are provided only along theouter edge of a column of micromachines.

[0027] Anchors 518 also are adapted to affix flexures from at least twomicromovers. Anchors 518 typically are provided only along the outeredge of a row 524 of micromachines. Similar to anchors 516, anchors 518are adapted to affix flexures from at least two micromachines. However,unlike anchors 516, each of which engages flexures on opposing sides ofthe anchor, each anchor 518 typically engages the flexures along oneside of the anchor.

[0028] Anchors 520 typically are provided at locations other than theouter periphery of an array of micromachines. As shown in FIG. 5,anchors 520 are adapted to affix flexures from at least fourmicromovers. In particular, one side of an anchor is adapted to affixflexures of adjacently disposed micromovers of a first row, and theother side of the anchor is adapted to affix flexures of adjacentlydisposed micromovers of a second row.

[0029] Although not shown in FIG. 5, separators also can be providedbetween at least some of the adjacently disposed micromovers of themicromachine system 100 depicted therein.

[0030] The foregoing description has been presented for purposes ofillustration and description. It is not intended to be exhaustive or tolimit the invention to the precise forms disclosed. Modifications orvariations are possible in light of the above teachings. The embodimentor embodiments discussed, however, were chosen and described to providethe best illustration of the principles of the invention and itspractical application to thereby enable one of ordinary skill in the artto utilize the invention in various embodiments and with variousmodifications as are suited to the particular use contemplated.

[0031] For example, spacing between adjacently disposed micromachinesmay not be required for micromachines that are intended to movetogether. In these embodiments, a further increase in packing densitycan be achieved by configuring these micromachines so that they engageeach other. All such modifications and variations are within the scopeof the invention as determined by the appended claims when interpretedin accordance with the breadth to which they are fairly and legallyentitled.

What is claimed is:
 1. A micromachine system comprising: a substratedefining a trench; a first microelectromechanical device arranged atleast partially within said trench, said first microelectromechanicaldevice including a first portion, said first portion being configured tomove relative to said substrate; and a second microelectromechanicaldevice arranged at least partially within said trench and adjacent tosaid first microelectromechanical device, said secondmicroelectromechanical device including a first portion, said firstportion being configured to move relative to said substrate.
 2. Themicromachine system of claim 1, further comprising: a first anchor fixedin position relative to said substrate, said first anchor beingconfigured to maintain said first portion of said firstmicroelectromechanical device at least partially within said trench; anda second anchor fixed in position relative to said substrate, saidsecond anchor being configured to maintain said first portion of saidsecond microelectromechanical device at least partially within saidtrench.
 3. The micromachine system of claim 1, further comprising: meansfor maintaining said first portion of said first microelectromechanicaldevice at least partially within said trench; and means for maintainingsaid first portion of said second microelectromechanical device at leastpartially within said trench.
 4. The micromachine system of claim 1,wherein said first portion of said first microelectromechanical deviceand said first portion of said second microelectromechanical device areconfigured to move independently of each other.
 5. The micromachinesystem of claim 1, further comprising: a separator disposed at leastpartially between said first microelectromechanical device and saidsecond microelectromechanical device, said separator being adapted toprevent said first microelectromechanical device from contacting saidsecond microelectromechanical device.
 6. The micromachine system ofclaim 1, further comprising: means for preventing said firstmicroelectromechanical device from contacting said secondmicroelectromechanical device.
 7. The micromachine system of claim 2,wherein: said first microelectromechanical device includes a firstflexure, said first flexure having a first end affixed to said firstanchor, said first flexure being affixed to said first portion of saidfirst microelectromechanical device, said first flexure being adapted todeform such that said first portion of said first microelectromechanicaldevice is capable of moving relative to said substrate; and said secondmicroelectromechanical device includes a first flexure, said firstflexure of said second microelectromechanical device having a first endaffixed to said second anchor, said first flexure of said secondmicroelectromechanical device being affixed to said first portion ofsaid second microelectromechanical device, said first flexure of saidsecond microelectromechanical device being adapted to deform such thatsaid first portion of said second microelectromechanical device iscapable of moving relative to said substrate.
 8. The micromachine systemof claim 5, wherein said separator is a micro-fabricated beam.
 9. Themicromachine system of claim 7, wherein said firstmicroelectromechanical device includes a second flexure, said secondflexure having a first end affixed to said second anchor, said secondflexure being affixed to said first portion of said firstmicroelectromechanical device; and wherein said secondmicroelectromechanical device includes a second flexure, said secondflexure of said second microelectromechanical device having a first endaffixed to said first anchor, said second flexure of said secondmicroelectromechanical device being affixed to said first portion ofsaid second microelectromechanical device.
 10. The micromachine systemof claim 7, further comprising: a third microelectromechanical devicearranged at least partially within said trench, said thirdmicroelectromechanical device including a first portion and a firstflexure, said first portion of said third microelectromechanical devicebeing configured to move relative to said substrate, said first flexureof said third microelectromechanical device having a first end affixedto said first anchor, said first flexure of said thirdmicroelectromechanical device being affixed to said first portion ofsaid third microelectromechanical device, said first flexure of saidthird microelectromechanical device being adapted to deform such thatsaid first portion of said third microelectromechanical device iscapable of moving relative to said substrate.
 11. The micromachinesystem of claim 8, further comprising: a separator disposed at leastpartially between said first microelectromechanical device and saidsecond microelectromechanical device, said separator being adapted toprevent said first microelectromechanical device from contacting saidsecond microelectromechanical device, said separator being adapted todeform in response to contact by said first portion of said firstmicroelectromechanical device and said first portion of said secondmicroelectromechanical device.
 12. The micromachine system of claim 8,wherein said first flexure of said first microelectromechanical deviceand said first flexure of said second microelectromechanical device aremicro-fabricated beams.
 13. The micromachine system of claim 10, furthercomprising: a fourth microelectromechanical device arranged at leastpartially within said trench, said fourth microelectromechanical deviceincluding a first portion and a first flexure, said first portion ofsaid fourth microelectromechanical device being configured to moverelative to said substrate, said first flexure of said fourthmicroelectromechanical device having a first end affixed to said firstanchor, said first flexure of said fourth microelectromechanical devicebeing affixed to said first portion of said fourthmicroelectromechanical device, said first flexure of said fourthmicroelectromechanical device being adapted to deform such that saidfirst portion of said fourth microelectromechanical device is capable ofmoving relative to said substrate.
 14. A method for forming an array ofmicromachines, comprising the steps of: providing a substrate; forming atrench in the substrate; arranging a first microelectromechanical deviceat least partially within the trench, the first microelectromechanicaldevice including a first portion configured to move relative to thesubstrate; and arranging a second microelectromechanical device at leastpartially within the trench, the second microelectromechanical deviceincluding a first portion configured to move relative to the substrate.15. The method of claim 14, further comprising the steps of: providing afirst anchor fixed in position relative to the substrate; maintainingthe first portion of the first microelectromechanical device at leastpartially within the trench with the first anchor; providing a secondanchor fixed in position relative to the substrate; and maintaining thefirst portion of the second microelectromechanical device at leastpartially within the trench with the second anchor.
 16. The method ofclaim 14, further comprising the steps of: providing a separator; andpreventing the first microelectromechanical device from contacting thesecond microelectromechanical device by arranging the separator at leastpartially between the first microelectromechanical device and the secondmicroelectromechanical device.
 17. The method of claim 14, wherein thefirst microelectromechanical device includes a first flexure, the firstflexure being adapted to deform; and further comprising the steps of:affixing a first end of the first flexure to the first anchor; andaffixing the first flexure to the first portion of the firstmicroelectromechanical device such that the first portion of the firstmicroelectromechanical device is capable of moving relative to thesubstrate.
 18. The method of claim 14, wherein the secondmicroelectromechanical device includes a first flexure, the firstflexure of the second microelectromechanical device being adapted todeform; and further comprising the steps of: affixing a first end of thefirst flexure of the second microelectromechanical device to the secondanchor; and affixing the first flexure of the secondmicroelectromechanical device to the first portion of the secondmicroelectromechanical device such that the first portion of the secondmicroelectromechanical device is capable of moving relative to thesubstrate.
 19. The method of claim 17, wherein the firstmicroelectromechanical device includes a second flexure, the secondflexure being adapted to deform; and further comprising the steps of:affixing a first end of the second flexure to the second anchor; andaffixing the second flexure to the first portion of the firstmicroelectromechanical device such that the first portion of the firstmicroelectromechanical device is capable of moving relative to thesubstrate.
 20. The method of claim 18, wherein the secondmicroelectromechanical device includes a second flexure, the secondflexure of the second microelectromechanical device being adapted todeform; and further comprising the steps of: affixing a first end of thesecond flexure of the second microelectromechanical device to the firstanchor; and affixing the first flexure of the secondmicroelectromechanical device to the first portion of the secondmicroelectromechanical device such that the first portion of the secondmicroelectromechanical device is capable of moving relative to thesubstrate.